Thermoelectric composition of matter containing silver, titanium, and a chalkogen



States s,iis,2si riiniuuouracraie CoMPosi'rIoN or corsrArNiNc snfvnn, TKTANIUM,

MATTER AND A atent and selenium was prepared by the following procedure: A homogeneous mixture comprising 4.000 parts silver, 1.776 parts titanium, and 5.8556 parts selenium was prepared by thoroughly blending the component (-200 @HALKQQEN I 5 mesh US. Standard Sieve Size) powders. This powder ji fp h iil 'i Nest g g gii gg igg mix was then sealed under vacuum in a quartz ampoule on g g gi measuring 15 mm. x 20 cm. The ampoule was slowly g ggg l E3241 3 E61 N0 80 W5 heated to 908 C. and this temperature maintained for a Ciaimg b i period of 12 hours. A crystalline reaction product resulted. This product was re ground and pressed into a This invention relates to new thermoelectric materials. 3 h X and the i Wes lehfed 1h vacuum It is an object of the present invention to produce ther- 111 PeFlOd 14 hollTS at 9 moelectric materials which are useful in devices Where a The Prodhet ehtelhed was to he thermally e Seebeck voltage (thermocurrent) is required. Such mato a temperature of at least 760 The reslshvlly of terials are substantially homogeneous crystalline prod- 15 the her was measured. R the 'g hleihed and Was ucts containing silver, titanium, and a chalkogen from found to be mlhlohm'embleemcfll energy was the group consisting of tellurium and selenium. When develoifed by hhthhg the h between two copilehblhcks the chalkoaen is tellurium, the atom ratio of silver, tita- ({haehlhed from the Same P 0f Sleek) melhtamed at m andhwuurium is 1:13 and when the chamugen different temperatures. The temperatures were measured is Selenium, the atom ratio is 1:19 at approximately the cross-sectional center of the bar The products of {his invention can be Prepared by fip immediately behind the contact faces. With a temperaing under inert conditions a powdered mixture of silver, ture hherehhal (AT) R 1= 's 2 titanium, and the chalkogen in the atom ratios indicated. ah of hhlhvohs Wes ehtalhedfile The duration of the firing period will vary, depending heck eeemeleht upon the reactants used, the size of the charge, and the 1000) equipment used in firing. The firing procedure used to AT Produce i111? P 9 of this invention is i was calculated from this data. This value and other and 0116 Sklllfid the art @311 ef y delehhlhe Optimum electrical properties are given in the table which follows firing time for any set of conditions. Firing causes an h examples increase in the volulrlne of the zclhariahand tliae produc XAMPL 11 obtained is a crysta ine materi w 10 can e presse I into a compact mass of desired shape for use in thermo- Usmg the sanle procedure as i p m Example electric applications. It is preferred to use as starting 3000 i Silver parts l 106461 materials commercially available reactants of highest puhalts teilunum each of 200 h parade were my and to have them in a mash (Standard screen thoroughly blended and sealed in an evacuated quartz ccale) Particle Size bfore firing ampoule. The ampoule was heated to 900 C., and this in a pyeferred method of prgpamtion the Products of temperature was maintained for 12 hours. The ampoule this invention are formed by grinding together silver, titag z the l g gemoved niuin, and either tellurium or selenium. If tellurium is mm 3 1 a POW er E wed in the grinding hum? the atom 0f Silva? to 40 pressed into a bar A x A X 2 and me bar retired in .s i m A v 1 O O n D titanium to tellurium should be 1:123. On the other vaculm for a or 12 hauls at bar hand if Seknium is usgd the atom ratio of the respec was tested for electrical properties, and these are sumtive aemoms Should The mixture gttainpd marized in the table below. The product was found to from the grinding operation is compacted into pellets and be thermally sftable to atileast fired under inert conditions at temperatures in the range The foiowmg table gives electrical data on h mata' Of 0 C m 11000 C for a period of 1 to 16 hours rials of Examples I and II. It has not been clearly estab- The product of this first firing cm be pressed into a dehshed Whether these new i hl are {me compounds sired shape for use in thermoelectric applications. Howaltho X'ray diffraction data m 52 presence ever, it is more desirable to regrind the product of the last 9 enmled. figure first firiru repress it into a desired shape, and refire to 1s a calculated figur whlcn In the sinter thimaterial into a s ron coheren end product art use to evaluate thermoelectric matenhisi .Thls figure g nn mi n 1 Sha e f0 a Whhh it is takes into account the fact that low resistivity and low 2 35 d O a p thermal conductivity as Well as high Seebeck coefficient For a clearer und rstandin the fo lowiir specific exare nsa'cessary for geod thiliemoeleotnc miltffial' The v v 55 equation for calculating the figure of ment is as folamples are given. These examples are intended to be lows: merely illustrative of the invention and not in limitation S2 thereof. Unless otherwise specified, all parts are by Z (figure of merit in C7 weight.

EXAMPLE 1 where r is the resistivity in ohm-cm, k is the thermal conductivity in watts per cm.-degree, and S is the Seebeck A thermoelectric material comprising silver, titanium, coeffic-ient in volts per degree. 1

Table Atom ratio Seebeck Resistivity Thermal Y Elements ofclenients Temp. at Temp. at coefficient in millicondue- Figure of Example Iyo. present; n incprnpocold face hot face in microohm-cm. tivity, merit in composition sition (Ti), 0. (T2), C. volts per (r) watts/deg. C.-

C. (S) cm.

I Ag, Ti, Se-.- 111:2 29 42 107 0.45 0.015 1.6GX10'3 1r Ag, Ti, To. 11:3 31 197 0.94 0.018 0. 59x10- From the thermoelectric properties given for the materials of this invention, it Will be evident that these materials are useful in thermoelectric generators. The measured properties also make it evident that these new compositions could be used for thermoelectric cooling by the Peltier effect.

Since it is obvious that many changes and modifications can be made in the above-described details Without departing from the nature and spirit of the invention, it is to be understood that the invention is not limited to said details except as set forth in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the production of a [thermoelectric composition of matter comprising firing in a closed system, at a temperature of from 700 C. to 1100" C. for a period of from 1 to 16 hours, a powdered mixture of silver, titanium, and a chalkogen from the group consist ing of tellurium and selenium, in an atom ratio of 1:1:3 when the chalkogen is tellurium, and in an atom ratio of 1:1:2 when the challcogen is selenium.

2. A process for the production of a thermoelectric composition of matter comprising firing in a closed system, at a temperature of from 700 C. to 1100 C. for a period of from 1 to 16 hours, a powdered mixture of silver, titanium, and a chalkogen from the group consisting of telluriu m and selenium in an atom ratio of 1:1:3 When the chalkogen is tellurium, and in an atom ratio of 1:1:2 when the chalkogen is selenium, and then recompaoting and refiring the product of the first firing.

3. A substantially homogeneous crystalline composition of matter having thermoelectric properties comprising silver, titanium, and a chalkogen from the group consisting of tellurium and selenium in an atom ratio of 1:1:3 when the chalkogen is tel lurium, and in an atom ratio of 1:1:2 when the chalkogen is selenium.

4. A substantially homogeneous crystalline composition of matter having thermoelectric properties comprisingsilver, titanium, and tellurium in an atom ratio of 5. A substantially homogeneous crystalline composition of matter having thermoelectric properties comprising silver, titanium, and selenium in an atom ratio of 1:1:2,

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR THE PRODUCTION OF A THERMOELECTRIC COMPOSITION OF MATTER COMPRISING FIRING IN A CLOSED SYSTEM, AT A TEMPERATURE OF FROM 700*C. TO 1100*C. FOR A PERIOD OF FROM 1 TO 16 HOURS, A POWDERED MIXTURE OF SILVER, TITANIUM, AND A CHALKOGEN FROM THE GROUP CONSISTING OF TELLURIUM AND SELENIUM, IN AN ATOM RATIO OF 1:1:3 WHEN THE CHALKOGEN IS TELLURIUM, AND IN AN ATOM RATIO OF 1:1:2 WHEN THE CHALKOGEN IS SELENIUM.
 3. A SUBSTANTIALLY HOMOGENEOUS CRYSTALLINE COMPOSITION OF MATTER HAVING THERMOELECTRIC PROPOERTIES COMPRISING SILVER, TITANIUM, AND A CHALKOGEN FROM THE GROUP CONSISTING OF TELLURIUM AND SELENIUM IN AN ATOM RATIO OF 1:1:3 WHEN THE CHALKOGEN IS TELLURIUM, AND IN AN ATOM RATIO OF 1:1:2 WHEN THE CHALKOGEN IS SELENIUM. 